Input control method and means for nitrogen oxide removal
AssigneesKurashiki Boseki Kabushiki Kaisha, Tokyo Shibaura Electric Co., Ltd.
InventorsRyoji Muraki, Shinichiro Takemura, Tetsuo Ai, Takaaki Kawasaki
Life of this patent
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Abstract
Nitrogen oxide contained in the flue-gas from a heating unit is removed in a nitrogen oxide removal unit by injection of nitrogen oxide removing agent in an amount determined by the amount of the nitrogen oxide contained in the flue-gas. Such amount of nitrogen oxide contained in the flue-gas is detected, on the one hand, by the estimation obtained through calculation using factors such as rate of supply of fuel to the heating unit and concentration of oxygen in the flue-gas, and on the other hand, by direct measurement, for a fail-safe system.
Claims17
In a method for removing nitrogen oxide (NO.sub.x) from flue-gas produced by a burner unit which is supplied with fuel, by an injection of NO.sub.x removing agent into said NO.sub.x removing means in an amount which is related to the amount of NO.sub.x included in said flue-gas, wherein said amount of NO.sub.x removing agent is controlled by a method comprising the steps of:
- (a) detecting at least two factors relating to burning requirements and burning conditions by respectively detecting means for producing signals indicative of said respective factors, said two factors being selected from flow rate of fuel to the burner unit, concentration of oxygen in the flue-gas, concentration of carbon dioxide in the flue-gas, flow rate of air used in the combustion process effected in the burner unit, and the amount of flue-gas;
- (b) calculating the amount of NO.sub.x contained in said flue-gas directed to said NO.sub.x removing means during a predetermined period of time by the application of said factors in a formula memorized in a computing means, said formula being changeable with respect to at least one of its constants;
- (c) measuring the amount of NO.sub.x contained in said flue-gas directed to said NO.sub.x removing means during said predetermined period of time by an NO.sub.x measuring means;
- (d) comparing the calculated amount of NO.sub.x with the measured amount of NO.sub.x by a first comparing means for evaluating the difference therebetween and
- (e) comparing the difference of step (d) with a predetermined range of tolerance for said difference by a second comparing means for producing a first signal when said difference is within the predetermined range and a second signal when said difference is outside said predetermined range;
- the improvement wherein the following steps are performed subsequent to step (e)
- (f) upon receipt of said second signal from said second comparing means, determining whether or not the NO.sub.x measuring means is in order by an inspection means for producing third signal when said NO.sub.x measuring means is in order and fourth signal when said NO.sub.x measuring means is out of order;
- (g) changing the factor of said formula of (b) in the computing means, upon receipt of said third signal from the inspection means for satisfying the formula to cause the calculated amount of NO.sub.x to be substantially equal to the measured amount of NO.sub.x ;
- and
- (h) controlling the amount of NO.sub.x removing agent to be injected into said NO.sub.x removing means in an amount in relation to the amount of NO.sub.x by controlling means, said controlling means using either the calculated amount of NO.sub.x or measured amount of NO.sub.x when either the first or third signals is applied thereto, and using the calculated amount of NO.sub.x when the fourth signal is applied thereto.
In an apparatus having means for removing nitrogen oxide (NO.sub.x) from flue-gas produced by a burner unit which is supplied with fuel, by an injection of NO.sub.x removing agent into said NO.sub.x removing means in an amount which is related to an amount of NO.sub.x included in said flue-gas, the improvment wherein there is provided means for controlling said amount of NO.sub.x removing agent comprising:
- (a) at least two detecting means for detecting at least two factors relating to burning requirements and burning conditions, respectively, and for producing signals from each of the detecting means indicative of respective detected factor;
- said two factors being selected from flow rate of fuel to the burner unit, concentration of oxygen in the flue-gas, concentration of carbon dioxide in the flue-gas, flow rate of air used in the combustion process effected in the burner unit, and the amount of flue-gas;
- (b) computing means connected to said two detecting means, said computing means memorizing a formula for calculating the amount of NO.sub.x contained in said flue-gas directed to said NO.sub.x removing means during a predetermined period of time by the application of said factors in said formula;
- (c) constant setting means connected to said computing means for setting at least one constant in said formula of (b) in the computing means;
- (d) NO.sub.x measuring means for measuring the amount of NO.sub.x containing in said flue-gas directed to said NO.sub.x removing means during said predetermined period of time;
- (e) first comparing means connected to said computing means and NO.sub.x measuring means for comparing the calculated amount of NO.sub.x with the measured amount of NO.sub.x and for evaluating the difference therebetween;
- (f) reference producing means for producing a reference signal indicative of upper and lower limits of a predetermined range of tolerance of said difference in (e);
- (g) second comparing means connected to said first comparing means and reference producing means for comparing the difference with the reference signal and for producing a first signal when said difference is within the predetermined range and second signal when the difference is outside the predetermined range;
- (h) means connected to said second comparing means and said NO.sub.x measuring means for determining, upon receipt of said second signal, whether or not the NO.sub.x measuring means is in order, and for producing third signal when said NO.sub.x measuring means is in order, and fourth signal when said NO.sub.x measuring means is out of order, and for supplying said third signal to said constant setting means for resetting said one constant in said computing means in reference to the difference produced by the first comparing means in step (e) and
- (k) controlling means for controlling the amount of NO.sub.x removing agent to be injected into said NO.sub.x removing means in an amount in relation to the amount of NO.sub.x, said controlling means using either the calculated amount of NO.sub.x or measured amount of NO.sub.x when one of the first and third signals is applied thereto, and using the calculated amount of NO.sub.x when the fourth signal is applied thereto.
Dependencies are inferred from the claim text.